1. Field of the Invention
The present invention relates to processing silver halide photographic materials, more particularly, to hardening color photographic materials with a bleach solution or a blix solution.
2. Description of the Prior Art
To rapidly process color photographic materials, it is generally necessary to process at a temperature higher than 30.degree. C., but in such a case the photographic emulsion layers of photographic materials are apt to be swollen and softened to cause reticulation or are apt to be scratched and peel off during processing. In fact, sometimes the emulsion layers melt during drying after processing. In particular, these faults tend to become more pronounced as the processing temperature is increased, and thus are a great obstacle to practice high temperature rapid processing.
To prevent softening of the emulsion layers of color photographic materials in high temperature processing thereof, a process has hitherto been employed wherein a hardening bath is used during processing or a hardening agent such as alum or formalin is added to another processing bath. The former process is, however, unsuitable for rapid processing since the number of processing steps increases and the time required to complete total processing is prolonged. On the other hand, the latter process is suitable for rapid processing since the number of processing steps and the processing time are the same as those of conventional high temperature processes. The process of this invention belongs to the latter type of processes.
Processing steps for silver halide color photographic materials include as necessary steps a silver removal step for removing silver images after color development. The silver removal step is usually composed of a bleach step and a fix step or a blix step which performs the bleach step and the fix step in one bath. In silver removal, silver formed by development is oxidized by a bleaching agent (oxidizing agent) to silver halide and the silver halide thus formed is converted into a water soluble silver salt by the fixing agent.
As the bleaching agent, potassium ferricyanide, potassium dichromate, and a metal complex salt of an organic acid are usually used. As potassium ferricyanide and potassium dichromate have a high bleaching power, they are used for bleaching color photographic materials containing a large proportion of silver, such as color negative films and color reversal films, but the demand for these materials has recently gradually been reducing due to the difficulty in treating water solutions containing these materials which cause water pollution. On the other hand, a metal complex salt of an organic acid can profitably be used in blix solutions since the complex salts causes less pollution problems and the treatment of waste solution containing such a complex salt is easy, and, further, it can be present together with a fixing agent due to the comparatively weak oxidative power thereof. Further, in the case of using the complex salt, the used processing solution can be easily regenerated by air oxidation for repeated use. Accordingly, metal complex salts of organic acids are widely used as excellent bleaching agents from the viewpoint of causing less pollution problems, simplicity of processing, capability of shortening the processing time and economic profitability.
It is known to incorporate a hardening agent in a bleach solution or a blix solution containing a metal complex salt of an organic acid as a bleaching agent, but with conventional techniques the usable hardening agents are quite limited since the effective pH range of the processing solution is in the weak acid or neutral region of 5.0 to 7.5, and, hence, a hardening agent which can only be used in an acid solution, such as potassium alum or chromium alum, cannot be used. Furthermore, it is also known to add an aldehyde compound such as formaldehyde or glutaraldehyde to such a processing solution, but in such a conventional process it is difficult to add a sufficient amount of the hardening agent to the processing solution to provide to the solution a hardening function which can endure high temperature processing since the addition of such a compound tends to deteriorate the stability of the solution to form precipitates during storage of the solution and has a bad influence on the photographic properties of color photographic materials processed therein to form fog during the storage of processed photographic materials.